See also the How to Use section.
Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.
Some products that may interact with this drug include: certain anti-depressants (e.g., fluoxetine, fluvoxamine, nefazodone), cimetidine, clozapine, digoxin, disulfiram, kava, ketoconazole, levodopa, omeprazole, phenytoin, sodium oxybate.
Tell your doctor or pharmacist if you also take drugs that cause drowsiness such as: antihistamines that cause drowsiness (e.g., diphenhydramine), anti-seizure drugs (e.g., carbamazepine), medicine for sleep (e.g., sedatives), muscle relaxants, narcotic pain relievers (e.g., codeine), psychiatric medicines (e.g., phenothiazines such as chlorpromazine, or tricyclics such as amitriptyline), tranquilizers.
Check the labels on all your medicines (e.g., cough-and-cold products) because they may contain drowsiness-causing ingredients. Ask your pharmacist about the safe use of those products.
This product can affect the results of certain lab tests. Make sure laboratory personnel and your doctors know you use this drug.
Smoking can decrease the effectiveness of this drug (through liver enzyme induction). Tell your doctor if you smoke or if you have recently stopped smoking because your dose may need to be adjusted.